How single-party primary elections are reshaping Congress

"I Voted" stickers are seen as a person casts their ballot in Philadelphia in Pennsylvania's primary on May 19. Matthew Hatcher/Getty Images hide caption

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Matthew Hatcher/Getty Images

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Congress could soon be more polarized than it already is. And primary elections are a big reason why.

Some lawmakers have begun to speak out against closed, single-party primaries, which they see as part of a system that limits voter choice and incentivizes elected officials to prioritize party loyalty over their own political judgment.

It's a case long made by advocates of primary reform.

"There has been a ratcheting up, a ramping up of both the willingness and the ability of both the Democrats and the Republicans to shape outcomes before the voters get a chance to have a say," John Opdycke, founder and president of the group Open Primaries, told NPR. "And that's really devastating."

In just the past several weeks, GOP primary voters in places like Indiana, Kentucky and Louisiana have forced out state and federal lawmakers who crossed President Trump, including on redistricting.

The critiques of party primaries come as the mid-decade redistricting efforts, initiated last year by Trump, have further reduced the number of competitive U.S. House districts.

More than 90% of seats are now considered relatively safe for one party or the other.

This means that primaries — which often are run by the parties themselves, exclude independent voters and see dramatically less participation than general elections — determine nearly all U.S. House members.

Nick Troiano, executive director of Unite America, has been pushing for states to hold nonpartisan primaries. He and other reformers have been warning that the mix of partisan gerrymandering and partisan primaries would lead to increased polarization in Congress.

"If you're an elected official, the only threat to your reelection is someone running to your ideological extreme in your primary," Troiano said. "And that has had the impact over many years, including this year, of meaning: If you're an independent-minded member of Congress, you're being basically hunted to extinction by the ideological flanks within both political parties."

"It's hurting our country"

Rep. Brian Fitzpatrick, R-Pa., testifies at a Senate hearing on Dec. 3, 2025. Andrew Harnik/Getty Images hide caption

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Andrew Harnik/Getty Images

Rep. Brian Fitzpatrick, R-Pa., represents a truly competitive district, a situation that often gives candidates the incentive to demonstrate their independence. Yet he says his state's closed primary process — in which only voters registered with a particular party can cast a ballot — precludes him from actually becoming a political independent.

He says closed primaries drag members of Congress away from compromise because they fear getting ousted by a more extreme opponent during the next primary cycle.

"You have so many people that are co-opted from doing the right thing and supporting the right policy because of politics," Fitzpatrick told NPR in April. "It's hurting our country."

While Pennsylvania does offer ways for independents to run in a general election, if Fitzpatrick chose to sit out the primary, he would face two major-party candidates instead of one in November, perhaps making his arduous race even more competitive.

"We should at least agree that every American citizen should never be denied the right to vote in every single election," he said, encouraging states and parties to embrace open primaries, in which all voters are free to participate.

But Fitzpatrick, who also backs a federal ban on partisan gerrymandering, ultimately wants to see even bigger reforms.

"Anybody that's taking an honest view of our government and has seen how the dysfunction has stifled and stymied progress knows that the two-party system is broken," he told NPR. "You cannot fit 340 million Americans in one of two boxes. You just can't. There are too many problems that are nuanced, a lot of gray area, to get the policy right."

Republican impeachment backer ousted in closed primary

It's not just House members who have problems with primary systems.

In 2021, Sen. Bill Cassidy, R-La., joined with Senate Democrats and six of his Republican colleagues in a vote to convict Trump on impeachment charges connected to Trump's effort to remain in office despite his 2020 election loss. Trump has worked ever since to drum the senator from office and recruited an opponent to run against him in this year's GOP primary.

But despite Louisiana's ruby red political lean, the president's endorsement alone may not have been enough to ensure Cassidy's defeat — until the state changed its election rules. Louisiana long had a kind of open primary for its Senate seats, in which all candidates, regardless of party, appeared on the same ballot and any registered voter could participate. If no single candidate got a majority of the votes, the top two candidates advanced to a head-to-head runoff.

In theory, that meant Democrats or voters not affiliated with a party could have chosen to support Cassidy in a strategic effort to prevent a more Trump-aligned replacement.

But ahead of this year's election, Louisiana's GOP-controlled legislature adopted a semi-closed system instead. When the primary was held in mid-May, only Republican voters — or unaffiliated voters who opted for a GOP ballot — were eligible to weigh in, precluding Cassidy from benefitting from crossover support.

Cassidy — who lobbied Democrats to change their party affiliation ahead of the primary vote — said the rule change was disenfranchising voters.

He lost soundly, finishing in third place with roughly 25% of the vote — and continued to speak out against a system that pushes politicians toward political extremes.

"Americans are exhausted by a culture that treats every disagreement as betrayal. Our constitutional system was designed around debate, persuasion, and compromise," Cassidy wrote on X.

Two primary systems, two different results

Sen. Lisa Murkowski, R-Alaska, speaks during a Senate hearing on May 19. Anna Moneymaker/Getty Images hide caption

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Anna Moneymaker/Getty Images

In 2010, Sen. Lisa Murkowski, R-Alaska, lost her state's primary to a hard-right challenger. The party's primary was only open to registered Republicans and unaffiliated voters.

Murkowski, more moderate than many of her GOP colleagues, chose to compete in the general election as a write-in candidate. The effort, which included a spelling bee television spot teaching people how to spell her last name, succeeded. Murkowski was the first senator in more than 50 years to win without her name on the ballot.

Like Cassidy, Murkowski voted to convict Trump on impeachment charges in 2021. Unlike the Louisiana senator though, Murkowski won reelection — after the state implemented changes to open up its primary process.

Since 2022, Alaska primary voters have used a single ballot on which all candidates for statewide offices appear. The top four candidates, regardless of party, advance to the general election. That year, Murkowski — apparently buoyed by the open primary system and other reforms — notched a narrow win in the general election.

She remains the only Republican senator who backed Trump's impeachment to win reelection.

Asked whether other states adopting an open, top-four primary system would benefit the Senate, Murkowski said, "I think it certainly benefits us in Alaska."

"Over 60% of the electorate [in Alaska] says, 'I don't like to align myself with either the Republican or Democrat Party,'" she said. "When you have closed primaries, it really limits to a very small number those who are eligible to participate."

Murkowski said top-four primary systems help to insulate lawmakers from pressure from political parties.

"Obviously the parties don't like that because they want control," she said. "I think it should be the people that are in control — and not the parties."

Few incentives to change

Advocates pushing for change say political parties are increasingly resistant to relinquishing control over primaries.

Opdyke, of Open Primaries, thinks the gerrymandering battle this year has supercharged interest among party leaders to close primaries.

"Now what we're seeing is that the parties have said, 'OK, we've gerrymandered the country into oblivion, there's not much more gerrymandering that we can do. Now we've got to start shutting down these open primaries,'" he explained. "And the Democrats are doing it and the Republicans are doing it."

For the past several years, Republicans across the country have been working to close their primaries. And recently, some Democrats have looked at doing the same. In California, with the possibility of two Republicans advancing from the gubernatorial primary, there is an effort underway to get rid of the state's nonpartisan primary system — one of the few in the country.

Troiano's Unite America group has been pushing for states to adopt systems similar to California. But in 2024, voters in a number of states rejected ballot measures that would have created nonpartisan primary systems, in a significant blow to reform movements.

Now, Troiano said, his organization is focused on fighting bills in about a dozen states that would close party primaries to independent voters.

He said he's also concerned that the bar for primary fights is getting lower. Troiano said it used to be that party members had to really be out of line with their party to get primaried.

"Today voting with your party 90% of the time now is sufficient reason to get a primary challenger and someone to replace you," he said.

This makes Congress worse

Opdyke said it is a common misperception that nonpartisan or open primary systems always lead to more moderate candidates.

But he argues that closed primaries disincentivize lawmakers from opposing sides from even working across the aisle on specific issues like energy and education.

"They can't sit down with them. They can't even be seen in the same room with them because the primary structure punishes any kind of collaboration, you know, heterodox activity," Opdyke said. "They cannot reach across the aisle. They can't build weird coalitions. They can't talk to people with whom they might disagree on 90% of issues, but they have overlap on 10."

In 2022, when NPR, PBS News and Marist last polled voters on whether they believe it is more important for government officials in Washington to "compromise to find solutions" or "stand on principle even if it means gridlock," roughly three-quarters preferred compromise.

Four years later, amid a brutal redistricting fight and even fewer competitive races, 86% of Americans say they disapprove of Congress' job performance.